1. Field of the Invention
This invention relates to extremely strong woven fabrics which give close to zero elongation in one direction. This invention also relates to abrasive belts made from said woven fabrics.
2. Description of the Prior Art
The extremely low elongation or yielding and extremely high strength under tensional stress, the substantially 100% elasticity, and the high resistance to heat exhibited by glass fibers have resulted in their increasing use in textiles which are subjected to dynamic stresses and/or high temperatures. For example, textiles which contain glass fibers are used as reinforcing materials for elastomeric products such as tires, industrial belts, mountings, shock absorbers and the like. For example, U.S. Pat. No. 3,695,326 teaches a tire fabric comprising glass fibers warp and weft which are bonded at their crossover points with a thermoplastic resin to preclude movement between the warp and fill fibers. The bond is treated with a resorcinol-formaldehyde reaction product for subsequent bonding to tire rubber. U.S. Pat. No. 4,073,330 teaches tire cord fabrics comprising alternating steel and glass fibers in the warp direction and synthetic fibers in the weft direction. The weft fiber is optional. U.S. Pat. No. 3,787,224 discloses glass fiber-reinforced elastomeric products wherein the glass fibers are coated with a specific resorcinolaldehyde composition to enhance bonding with the elastomeric material. U.S. Pat. No. 4,103,102 discloses a polyester/glass woven fabric which is impregnated with resin and used in wiring boards. U.S. Pat. No. 4,001,477 discloses phenol-formaldehyde fibers which are woven with glass fibers to produce a flame resistant fabric for the manufacture of clothing. However, these fabrics are either too stiff, would elongate excessively, would self-destruct, or are too bulky for the production of industrial belts which are subjected to high speeds and high horsepower, or for the production of abrasives which are suitable for precision abrading operations.
The use of textiles, both woven and nonwoven, which contain glass fibers in the production of polishing and abrasive products such as burnishing wheels, abrasive belts and abrasive disks is well-known. U.S. Pat. Nos. 2,404,207, 2,808,688 and 3,146,560 disclose abrasives which contain nonwoven glass fibers. U.S. Pat. No. 2,763,105 discloses a burnishing wheel comprising a glass fabric impregnated with a thermosetting resinous binder. However, these abrasives are either not flexible or, if flexible, elongate excessively or disintegrate rapidly upon use in abrasive operations. They are not well suited for precision grinding and require subsequent costly milling operations.
Abrasive belts comprising glass fabrics which are coated with a phenol-formaldehyde resin and abrasive particles are disclosed in U.S. Pat. Nos. 2,138,882 and 2,740,239. In the latter patent, the use of one fiber type is preferred so as to eliminate differences in strength. However, abrasive belts which contain only glass fibers in both the warp and fill directions are rapidly destroyed in heavy abrasive operations, such as the debarking of logs, because adjacent glass fibers rub each other along their length resulting in breakage of the glass fibers. Also, glass fibers which are transverse to each other tend to cut each other at crossover points. The use of synthetic fibers in the fill direction to reduce destruction of warp glass fibers at crossover points is disclosed in U.S. Pat. Nos. 2,372,983, 2,477,407 and 3,073,004. However, the warp glass yarns can still cut each other due to rubbing along their length.
Replacement of a portion of the warp fibers of a woven, non-glass fiber fabric to increase the wet strength of the fabric is disclosed in U.S. Pat. Nos. 2,329,452, 2,370,946 and 2,400,327. In U.S. Pat. No. 2,329,452 the wet strength is increased and the stretch or shrinkage factor is kept below 1 to 2% in a textile fabric by alternating cotton and spun rayon threads in the warp direction. In U.S. Pat. No. 2,370,946 fabrics are oiled or varnished to render them suitable for electrical insulating purposes. Yarns of high extensibility and yarns of low extensibility in both the warp and weft directions are alternated to minimize tearing due to cutting action between the stronger yarns. U.S. Pat. No. 2,400,327 teaches that the wet strength of rayon fabric is increased by alternating rayon fibers with another fiber such as cotton in the warp direction. However, without glass fibers, the fabrics of these patents would elongate, and thus be unsuitable for the manufacture of abrasive belts used for debarking logs and other purposes where low-stretch is essential for abrasive belts.
Abrasive and polishing materials which contain woven non-glass fabrics are disclosed in U.S. Pat. Nos. 2,672,715, 3,597,887, 3,688,453, 3,706,167 and 3,787,273. U.S. Pat. No. 3,597,887 discloses a buffing wheel comprising a fiberglass mesh impregnated with an abrasive-containing foamed adhesive. U.S. Pat. No. 3,706,167 discloses a flap wheel comprising a woven fabric, and an abrasive material coated thereon. In U.S. Pat. No. 2,672,715 crimps are made in the longitudinal strands of the abrasive belt so as to reduce stretching of the belt. U.S. Pat. No. 3,688,453 discloses an abrasive belt having a woven scrim cloth backing which may be of polyester or nylon. A non-woven layer is laminated on the woven layer. A resin containing an abrasive impregnates the woven and non-woven layers. It is disclosed that the abrasive belt should not stretch more than 5 percent. U.S. Pat. No. 3,787,273 discloses an abrasive belt having low stretch characteristics wherein a heavy woven fabric is used as a backing for the belt. However, these products do not possess the close to zero elongation and high strength which can be achieved with woven fabrics which contain glass fibers in the direction of tensional stress.
Glass fabrics comprising glass fibers and synthetic fibers in one direction are disclosed in U.S. Pat. Nos. 2,951,277, 3,707,120, 3,855,678 and 3,919,018. In U.S. Pat. No. 2,951,277 a fabric having controlled stretch is achieved with synthetic fibers and glass fibers in the warp direction. U.S. Pat. Nos. 3,707,120, 3,855,678, and 3,919,018 (all to C. F. Schroeder) teach a woven sheet, good for the reinforcement of rubber products, such as industrial belts, wherein warp glass filament strands are spaced regularly between warp strands of extensible organic filaments and all weft or fill strands are of an organic material such as nylon. The glass strands are impregnated with an organic resin latex containing resorcinol-formaldehyde resin. The fabric features a pattern of weave characterized in that the glass fibers in the warp direction exhibit a frequency of ups and downs which is greater than the frequency of ups and downs of the yarns of greater extensibility in the warp direction. As a result, the fabric stretches in the warp direction until the glass fibers are straight, or in alignment with the direction of tensile force. Abrasive belts made with stretchable fabrics such as disclosed in U.S. Pat. No. 2,951,277 and in the Schroeder patents would not exhibit the close to zero elongation which is needed for highly precise abrasion operations.
According to the present invention, there is provided a fabric which exhibits close to zero elongation and extremely high strength under tensional forces. The present invention also provides abrasive products which exhibit close to zero elongation, high strength and long lives even when used in vigorous abrading operations such as the debarking of logs.